1. Field of the Invention
This invention relates to wheeled vehicle support devices and more particularly to a novel apparatus by which a single wheel ground contact area can be increased employing a flotation augmentation means.
2. Brief Description of the Prior Art
Numerous attempts have been made to improve the soft-soil and snow performance of wheeled vehicles. In the case of conventional wheeled vehicle designs, for example, automobiles, trucks, and farm tractors, emphasis has been placed on the grouser effect of chains and the like to improve thrust by a soil shearing action. While this approach has enjoyed a measure of success with powered driving wheels, unpowered wheels on trailers, aircraft, farm implements, and construction equipment have represented a compromise in terms of tire and wheel design. On the one hand, the desirable goal of a relatively high-pressure tire for operation on improved surfaces such as paved roads and airfields conflicts with tire characteristics desired, on the other hand, in soft soils and snow. In the latter conditions, increased ground contact area and greater flotation are essential. It is a well known principle in soil mechanics that increasing the lengthwise dimension of the ground contact area is significantly more effective mobility-wise than increasing the width of said contact area.
The compromises afforded the designer up until now have, however, been limited, and in applications demanding a minimum volume running gear, such as an aircraft landing gear, the high-pressure tire, minimum envelope approach has prevailed. This situation of course, has restricted high-performance aircraft, for example, to ground operations on improved surfaces. Likewise, the characteristic stress concentrations on these improved surfaces dictates the depth and composition of the subgrade as well as the thickness of the pavement and base.
If considered in a strict military context, the limited ground mobility, or limited ability to traverse anything short of an improved paved surface represents a serious limitation for today's military aircraft. Additionally, the vulnerability of the high pressure, heavily loaded tire to damage or failure from rocks and debris argues in favor of some form of protective barrier.
Therefore, a longstanding need has existed especially related to aircraft, to provide a flotation device for single and dual wheels to increase ground contact area, ideally, in a lengthwise manner, and also to serve as a protective barrier from rocks, debris, and the like.